1. Field of the Invention
The present invention is a display device, for use on a multi-speed (multi-gear) bicycle, which displays the currently selected bicycle gear.
2. Art Background
The derailleur equipped bicycle is by far the most common type of multi-speed bicycle available today. These comprise between 5 and 8 sprockets (also known as cogs, a cluster, or more generally as gears) mounted on a freehub at the rear wheel of the bicycle and between 1 and 3 chainrings attached to the bicycle crank. By varying the combinations of front chainring and rear sprocket that are connected by the bicycle chain, a wide range of gear ratios may be obtained. This is accomplished by the use of front and rear derailleurs respectively. A problem inherent in this system is the difficulty involved in determining what gear the bicycle is in at a given moment. To do this, the rider must observe the chainrings and sprockets. Positioned between the rider's legs, the front chainrings are fairly easy to see and, with the relatively small number of chainrings, it is often possible to remember which chainring the chain is engaging. The rear sprockets are by contrast rather difficult to see from a riding position. In trying to view the sprockets, a rider must take his eyes off the road and engage in a series of contortions while also interrupting his pedaling cadence. The dangers and inconveniences of this are readily apparent.
To solve this problem, a gear indicator is required which is located in a position that is easily viewable. In the prior art, a number of solutions have been proposed. These have generally involved either using a shift lever itself as the indicator, or connecting an indicator thereto. The first case is illustrated in U.S. Pat. No. 4,924,723 to Cristie. Cristie relates to a very simple stem mounted stick shifter. A lever is mounted substantially vertically and rotates about a horizontal shaft. The shift cable is mounted to a shorter arm of the lever which extends downward from the shaft. A longer upward extending arm is manually rotated to change gears. The arm protrudes through a slot in a housing. Numerals are inscribed on the housing along the slot. The numerals are positioned to line up with the arm when the bicycle is in the corresponding gear.
Examples of the second situation can be seen in U.S. Pat. Nos. 3,524,979 to Cohen and 4,586,396 to Nagano. As does Cristie, Cohen relates to a stick-type shifter. The stick is mounted on a horizontal shaft onto which a pulley is also mounted. The shift cable end is fixed relative to the pulley so that rotation of the shift will wrap or unwrap the cable from the pulley. The pulley is integrated with a driving gear which meshes with a smaller driven gear which in turn drives a rotary display via a flexible shaft (a spring bent 90 degrees).
Nagano relates to an improved arrangement for downtube mounted shift levers. Although shift levers have generally been disposed on opposite sides of the downtube, for ergonomic considerations Nagano places them atop the downtube and thus adjacent to one another. The patent's drawings further disclose a display member which is used to indicate which rear sprocket the chain engages. Although not a subject of the claims, nor described in detail in the specification, the display member appears to take the form of numerals inscribed on a ring disposed between two shift levers, along their axis of rotation. Adjacently attached to the rear derailleur lever is a gear of radius slightly larger than the ring. The outer circumference of the ring is toothed. Meshing with the ring teeth and lever gear is a small gear having two sections, one section necessarily of lesser radius than the other. By this mechanism, the rotation of the ring is amplified relative to that of the lever.
An electronic gear display is provided in U.S. Pat. No. 4,859,984 to Romano. Romano discloses the use of sensors attached to shift levers to determine the engaged gear. The sensors are connected to an electronic display. The sensors use a series of switch contacts disposed on the levers so that the contacts are selectively connected according to lever position.
All known prior art references for gear indicator devices require integration of the device with the shift lever (or knob, etc.) mechanism. All such devices require that either the indicator itself or gear position sensor be integrated with the shift lever. Due to the required integration, these devices are not suitable for aftermarket installation. Furthermore, as the shift levers on modern bicycles are located in a variety of places (downtube, handlebar, stem and handlebar-end mounted configurations predominating), the devices that require integration do not have the abilities to adapt to the various configuration. Finally, with the introduction of ratcheting or so called push-button shifters which are now prevalent on mountain bicycles (MTBs) use of the lever itself as an indicator is no longer feasible, as its position is unrelated to the engaged gear.